Increasing concern over the environmental fate of plastic materials has prompted considerable research into ways to increase the biodegradation of such products. As part of this effort, catalysts have been sought which would increase the rate of photooxidation of oxidizable polymers. It is known that white pigments vary greatly in their photooxidation activities, and that these pigments can significantly influence the weathering rates of polymers in which they are incorporated (see, for example Irick, et al., ACS Adv. in Chem. Series #151, pp. 147-162 (1981); Irick, et al., "Durability of Building Materials and Components", ASTM STP 691, P. J. Sereda and G. G. Litvan, Eds., ASTM, 1980, pp. 853-862; Irick, et al., "Prediction of the Influence of Titanium Dioxide on Polymer Weathering", Permanence of Organic Coatings, ASTM STP 781, pp. 35-42 (1982); H. G. Volz, et al., ACS Symp. Series 151, "Photodegradation and Photostabilization of Coatings", ACS, Washington, 1981, 163-182; and J. Lacoste, et al., J. Polym. Sci. Part A, 25 (10 ), 2799-2812 (1987)). Further, U.S. Pat. No. 4,022,632 teaches that pigment activities can be lowered by the addition of various metals to their surfaces. The present invention, as described below, provides novel pigments which markedly enhance the rate of photodegradation of oxidizable polymers. These pigments are comprised of anatase titanium dioxide containing metal salts of sulfuric acid or phosphoric acid.